ichthyomancy

from The Collaborative International Dictionary of English v.0.48

Ichthyomancy \Ich"thy*o*man`cy\, n. [Gr. 'ichqy`s, -y`os, a fish
   + -mancy: cf. F. ichthyomancie.]
   Divination by the heads or the entrails of fishes.
   [1913 Webster]